Auto-sequentially commutated current-source inverter (ASC-CSI) is a system known to produce a unidirectional DC current in a link between an AC-DC converter and an inverter. See for instance "Current-Source Converter for AC Motor Drives" by Kenneth P. Phillips in IEEE Trans. Ind. Appl., vol. IA-8, pp. 679-683, Nov./Dec. 1972. In this system, control of the inverter with thyristors amounts to steering the direct current of the DC-link through any one of six paths in the machine. Commutation from one path to the next is achieved with the aid of auxiliary commutation capacitors and blocking diodes.
It is also known from U.S. Pat. No. 4,648,022 to use three groups of three bilateral switches controlled between a three-phase AC power supply and the three phases of an AC motor controlled according to a switch polarity pattern exhibiting a "hidden DC-link" so as to supply AC power to an AC motor. The "hidden DC-link" also appears in FIG. 7 of U.S. Pat. No. 4,002,958, where an inverter configuration is achieved with six groups of three unidirectional switches.
It is now proposed to establish a current-source converter for an AC motor drive without using a converterinverter combination like in the Kenneth P. Phillips article, thus, without having a DC-link, but rather to apply directly the AC power supply, through a matrix-type set of a bilateral static-controlled switches, making use of an hidden DC-link like found in U.S. Pat. No. 4,648,022, to the AC motor.